Transformer



July 18, 1939. A, D. MA ET AL 2,166,613

TRANSFORMER Filed Oct. 26, 1936 ATTORNEYS.

Patented July 18, 1939 UNITED STATES PATENT OFFICE.

bus, Ind., assignors to Noblitt-Sparks Industries,

Inc., Columbus, Ind., a. corporation of Indiana Application October 2.6, 1936, Serial No. 107,502

3 Claims.

Our invention relates to the construction of transformers of the type used in coupling adjacent stages of a radio-receiver. It is our object to produce a transformer in which each winding may be adjusted to vary its inductance and thereby to tune the associated circuit and in which the two windings may be adjusted relatively to each other to vary their mutual inductance, A further object of our invention is to produce a transformer which will be of rugged construction and therefore suitable for use in automobile radio-receivers. Still another object of our invention is to provide a. transformer which may be simply and economically manufactured.

In carrying out our invention, we form each of the two windings of the transformer of two separate coils wound independently upon sleeves of insulating material which, in the assembled transformer, are slidably mounted on an axially extending column. Supported from this column at the sides of the coils are a plurality of longitudinally extending rods. of conducting material to which the leads from the various coils are secured, four of such rods serving as terminals for electrical connection in the coupled circuits of the radio receiver. The leads interconnecting the coils and rods are sufficiently long to permit independent axial movement of each coil on the central column, whereby the inductance of each winding of the transformer and the mutual inductance of both may be varied within such limits as are necessary to provide tuning of the respectively associated circuits and to secure the desired coupling. After the coils have been placed in their proper respective positions, the assembly is dipped in a liquefied insulating material which, when it solidies, will prevent any relatively axial movement of the coils.

The accompanying drawing illustrates our invention: Fig. 1 is an axial section through the enclosing shield of the transformer, all parts but the shield being shown in front elevation; Fig. 2 is a view similar to Fig. 1 except that the parts of the transformer, with the exception of the shield, are shown in rear elevation; Fig. 3 is a diagrammatic illustration showing one Way in which the transformer may be connected in a radio-receiver; and Fig. 4 is a fragmental longitudinal section on an enlarged scale illustrating a detail of construction.

The transformer shown in the drawing is provided with a cylindrical shield or an enclosing shell ID of conducting material having an open end in which is mounted a closure II of insulating material. Attached at the center of the closure I I is an axially extending cylindrical column I 2 of insulating material, conveniently a cardboard tube, and near the longitudinal center of this tube we provide a disk-shaped head I3 of insulating material held in fixed position on the tube as by having a press fit thereon. The two windings. of the transformer are supported from the column I2 on opposite sides of the head i3.

As previously indicated, each winding of the transformer comprises two separate coils. In the arrangement illustrated in the drawing, the primary of the transformer is disposed above the head I3 and comprises two coils I5 and IB wound respectively on sleeves il and I8 of insulating material which fit the column I2 rather snugly but not too tightly to prevent them from being moved therealong. The secondary of the tran..- former, which is located below the head I3, comprises two coils ZE) and 2I mounted respectively on sleeves 22 and 23 similar to the sleeves II and I8.

For the purposes of interconnecting the two coils of each winding and of providing for the connection of the windings to outside circuits., a

plurality of longitudinally extending rods of conducting material are mounted in the closure II and head I3. These rods may be disposed at any desired angular intervals about the axis of the column I2, but the arrangement illustrated in the drawing is preferred. In that arrangement two diametrically opposite rods 25 and L25 extend through the closure II and head I3 and project upwardly well beyond the head I3. Another pair of diametrically arranged rods, indicated at 2l and 28, extend through the end closure II and upwardly into association with the head i3, but do not extend vertically beyond such head. A third pair of rods 30 and 3l project axially in opposite directions from the head I3. All the rods mentioned are desirably located in angularly spaced relation, the rods 2l and 23 being spaced at from the rods 25 and 26, while the rods 30 and 3l may be located diametrically opposite each other and angularly intermediate the other four rods.

We iind it desirable to attach the various rods to the head I3 in some way which will prevent their axial movement relative to the head. To this end, the head I3 may be provided with a metal eyelet 35 (see Fig. 4) at each point where a rod is to pass through it; and, after each rod has been properly positioned in its associated eyelet, it is soldered thereto.

The leads from the various coils are attached, desirably by soldering, to the various rods 25, 26,

21, 28, 30, and 3I which thereby afford the necessary connection between the coils of each winding and provide for the connection of the two windings to outside circuits. As indicated, the lead All from the inside of the upper coil I5 of the primary winding is soldered to the rod 25, while the lead 4I from the outer end of such coil is soldered to the rod 3|. The lead 42 from the inner end of the other coil I6 of the primary winding is soldered to the rod 3I, while the lead 43 from the outer end of the coil I6 is soldered to the rod 26. Thus, the two coils I5 and I6 are connected together through the rod 3I, while the ends of the primary winding are connected to the two rods 25 and 26 which extend outwardly through and beyond the closure II for connection to outside circuits.

Below the head I3, the lead 44 from the outside of the coil 20 and the lead 45 from the inside of the coil 2l are soldered to the rod 3U to connect the two coils 2U and 2I together, while the lead 46 from the inside of the coil 26 and the lead 41 from the outside of the coil 2| are connected respectively to the two rods 21 and 28.

As is customary, we associate with each winding a iixed condenser, the condenser 5U for the primary winding being disposed above the head I3 with its leads soldered to the rods 25 and 26, respectively. The condenser 5I associated with the secondary winding is disposed below the head I3 and has its leads soldered respectively to the rods 21 and 28.

In Fig. 3 we have shown the transformer of Figs, l and 2 used to couple two stages of intermediate-frequency amplification in a radio receiver of the superheterodyne type. The rod 25 is connected to the plate 55 of the tube in the vfirst of such stages, while the rod 26 is connected to the positive side of the source of B-voltage. On the secondary side of the transformer the rod 223 is connected to the grid 56 of the tube in the second intermediate-frequency stage, while the rod 2l is connected to ground, this connection being shown as through a xed condenser 51 provided for the purpose of isolating the grid 56 so that a Variable bias can be imposed thereon through a lead 58 to provide automatic volume control.

The sleeves I1, I8, 22, and 23, on which the coils E5, I6, 26, and 2| are wound, are made of such lengths and the coils are respectively disposed upon them in such positions as to insure that the relative locations of the coils will be approximately correct when the device is assembled. By adjusting-the two coils of each winding toward or away from each other, the inductance of that winding may be varied in order to tune the circuit with which it is associated to the proper frequency; and, after this result has been accomplished, either winding may be moved as a unit relatively to the other to bring to the desired point the coupling of the two stages. All

the leads from the Various coils are sufficiently long to permit such adjustment of the coils as is necessary. After the coils have been brought to the proper respective positions, the assembly is immersed in a liqueiied insulating material which, when it solidiies, will serve to prevent accidental displacement of any coil. After this operation has been performed, the transformer is ready for insertion in the shield I0, it being held in place therein by securing the closure II in place in any desired manner.

We claim as our invention:

1. A transformer for coupling two stages of a radio receiver, comprising a central column of insulating material, two pairs of sleeves of insulating material slidable on said column, a coil mounted on each of said sleeves and movable therewith, a member of insulating material secured to one end of said column, a head secured to said column between said two pairs of coils, a pair of rods of conducting material secured toy said head and extending oppositely therefrom into association respectively with said two pairs of coils, each of said rods being connected to one end of each of the two coils with which it is associated, a second pair of rods extending between said head and member and projecting outwardly beyond the latter, the remaining ends of the two coils between said head and member being connected respectively to said second pair of rods, and a third pair of rods extending between said head and member and projecting axially beyond both, said third pair of rods being connected respectively to the remaining ends of the other two coils.

2. The invention set forth in claim l with the addition that said rods are disposed in angularly spaced relation about the axis of said column and substantially parallel thereto.

3. A transformer for coupling two stages of a radio receiver, comprising a central column of insulating material, two pairs of coils axially slidable on said column, a member of insulating material secured to one end of said column, a head secured to said column between said two pairs of 4 coils, a pair of rods of conducting material secured to said head andextending oppositely therefrom into association respectively with said two pairs of coils, each of said rods being connected to one end of each of the two coils with which it is associated, a second pair of rods extending between said head and member and projecting outwardly beyond the latter, the remaining ends of the two coils between said head and member being connected respectively to said secing between said head and member and projecting axially beyond both, said third pair of rods being connected respectively to the remaining ends of the other two coils.

ALBERT D. SILVA. BENJAMIN H. IRWIN.

n55 ond pair of rods, and a third pair of rods extend- 

